Determination of Monthly Hydrological Erosion Severity and Runoff in Torogh Dam Watershed Basin Using SWAT and WEPP Models

Evaluation of runoff and sediment load is the main problem that affects the performance of dams due to the reduction in the storage capacity of their reservoirs and their effect on dam efficiency and operation schedule. Hydrologic models are increasingly used for simulation of spatially varied hydrologic processes with the availability of spatially distributed data to understand and manage natural and activities that affect watershed systems if the continuous field measurements are not available. Soil and water conservation and also quantification of soil loss in watershed basins are a significant issue. In this study, the Soil and Water Assessment Tool (SWAT) and the Water Erosion Prediction Project (WEPP) are applied to estimate runoff volume and sediment load for Torogh dam reservoir area that is located in Kashafrood Watershed Basin in northeastern Iran. Simulated and observed runoff and sediment load are compared with these models. In the calibration period, the Nash–Sutcliffe coefficient (NSE) values for the SWAT and WEPP were 0.698 and 0.854 for runoff, and 0.667 and 0.832 for sediment load, respectively. In the validation period, the NSE values for SWAT and WEPP were 0.678 and 0.824 for runoff, and 0.809 and 0.816 for sediment load, respectively. The results indicate that both models gave reasonable results in comparison with measured values. Simulation with WEPP model was better than SWAT in some cases and with reasonable confidence could be used for soil loss quantification in the watershed basin of Torogh dam.